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nvme_disk: Allocate and utilize qpairs based on how many CPUs we have.

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This replaces the previous round-robin system. It should reduce
lock contention on multi-core systems, with potential other
benefits depending on drive behavior.

FreeBSD's NVMe driver does basically the same thing.
This commit is contained in:
Augustin Cavalier 2021-10-27 13:38:28 -04:00
parent 18851359d0
commit 9bc2885cd4
1 changed files with 21 additions and 11 deletions
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32
src/add-ons/kernel/drivers/disk/nvme/nvme_disk.cpp
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@ -71,7 +71,7 @@ static const uint8 kDriveIcon[] = {
#define NVME_DISK_DEVICE_MODULE_NAME "drivers/disk/nvme_disk/device_v1"
#define NVME_DISK_DEVICE_ID_GENERATOR "nvme_disk/device_id"
#define NVME_MAX_QPAIRS (8)
#define NVME_MAX_QPAIRS (16)
static device_manager_info* sDeviceManager;
@ -89,18 +89,17 @@ typedef struct {
uint32 max_io_blocks;
status_t media_status;
struct qpair_info {
struct nvme_qpair* qpair;
} qpairs[NVME_MAX_QPAIRS];
uint32 qpair_count;
uint32 next_qpair;
DMAResource dma_resource;
sem_id dma_buffers_sem;
rw_lock rounded_write_lock;
ConditionVariable interrupt;
struct qpair_info {
struct nvme_qpair* qpair;
} qpairs[NVME_MAX_QPAIRS];
uint32 qpair_count;
} nvme_disk_driver_info;
typedef nvme_disk_driver_info::qpair_info qpair_info;
@ -274,8 +273,17 @@ nvme_disk_init_device(void* _info, void** _cookie)
}
// allocate qpairs
info->qpair_count = info->next_qpair = 0;
for (uint32 i = 0; i < NVME_MAX_QPAIRS && i < cstat.io_qpairs; i++) {
int32 try_qpairs = cstat.io_qpairs;
try_qpairs = min_c(try_qpairs, NVME_MAX_QPAIRS);
if (try_qpairs >= smp_get_num_cpus()) {
try_qpairs = smp_get_num_cpus();
} else {
// Find the highest number of qpairs that evenly divides the number of CPUs.
while ((smp_get_num_cpus() % try_qpairs) != 0)
try_qpairs--;
}
info->qpair_count = 0;
for (uint32 i = 0; i < try_qpairs; i++) {
info->qpairs[i].qpair = nvme_ioqp_get(info->ctrlr,
(enum nvme_qprio)0, 0);
if (info->qpairs[i].qpair == NULL)
@ -288,6 +296,9 @@ nvme_disk_init_device(void* _info, void** _cookie)
nvme_ctrlr_close(info->ctrlr);
return B_NO_MEMORY;
}
if (info->qpair_count != try_qpairs) {
TRACE_ALWAYS("warning: did not get expected number of qpairs\n");
}
// allocate DMA buffers
int buffers = info->qpair_count * 2;
@ -396,8 +407,7 @@ nvme_interrupt_handler(void* _info)
static qpair_info*
get_qpair(nvme_disk_driver_info* info)
{
return &info->qpairs[atomic_add((int32*)&info->next_qpair, 1)
% info->qpair_count];
return &info->qpairs[smp_get_current_cpu() % info->qpair_count];
}